Pulsed field ablation device and method

ABSTRACT

An ablation device and method for pulsed field ablation, the device comprising a catheter including an expandable basket, a set of electrodes formed on the expandable basket, and a pulse generator suitable for generating electric pulses wherein the pulse generator being in electrical connection with the set of electrodes. The expandable basket is formed of a braided mesh of filaments, wherein the filaments are made of nonconductive material, wherein at least portion of the filaments comprises a lumen, wherein the filaments further include electrodes and conductive wires. The conductive wires at least partially lead inside of the lumen of the filaments and are electrically connected to the electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 17/931,975, filed on Sep. 14, 2022, which is a continuation of PCT/1132022/000189, filed on Jun. 4, 2022, which claims priority to US Provisional Patent Application Nos. 63/171,832, filed on Apr. 7, 2021; 63/218,563, filed on Jul. 6, 2021; and 63/249,965, filed on Sep. 29, 2021, all of which are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to ablation devices and methods, specifically devices and methods of pulsed field ablation of a target tissue by pulsed electric fields where one of the main principles of the ablation may be an irreversible electroporation of cell membranes.

BACKGROUND OF THE INVENTION

Atrial fibrillation is the most common persistent cardiac arrhythmia, affecting 10% of the population over 60 years of age. In addition to pharmacological treatment, the established therapy to improve the symptoms of the disease and reduce mortality is so-called catheter ablation.

Catheter ablation involves subcutaneously advancing one or more flexible catheters into the patient's blood vessels, in case of a heart ablation usually either in a femoral vein, an internal jugular vein, or a subclavian vein. The catheters are then advanced towards the target treatment site in or on the heart.

The primary means of ablation therapy of cardiac arrhythmias is to eliminate the pro-arrhythmogenic substrate directly by destroying it or to prevent the spread of non-physiological action potential by linear or circular isolation. Both of these approaches basically require the formation of a lesion through which the action potential of the myocardium does not spread. By applying energy, a small part of the myocardium is locally destroyed and is transformed into non-myocardial connective tissue by natural physiological processes within several weeks.

Common methods of ablation known from the prior art are based on thermal destruction of the tissue either by high or by low temperatures. Such methods include for example heating a target tissue by radiofrequency field (RF) or laser, or freezing the tissue by cryoablation. Those methods cause necrosis of the target tissue, which can add risk to the procedure.

Recently, methods and devices using electric fields for ablation have been utilized. The goal of these methods is to cause tissue destruction by inducing an irreversible electroporation of cell membranes instead of destruction by high or low temperatures, and so reduce the disadvantages and risks of ablation procedures based mainly on thermal damage, however there are still drawbacks that need to be solved.

Common design of such devices may be a catheter with a distal tip with one or more electrodes. The catheter can have for example one active electrode on the tip. An indifferent electrode can be placed for example on the skin of a patient. Ablation of the target treatment site with such a device has to be done point by point, which increases the duration and complexity of the procedure.

Another example of a prior device is a catheter with electrodes placed in a row on a distal tip of a single catheter body. The distal tip of such catheter is delivered close to the target treatment site and deployed (bent) into a specific shape near the target treatment site. With such a shape, more than one electrode can be used for the therapy and less movement with the distal tip is needed, but the deployment of the catheter into the right shape, proper positioning and further manipulation with such a catheter can be very difficult. An indifferent electrode can be placed on the skin of the patient as well or the ablation can be carried out in bipolar fashion between particular electrodes placed on the distal end of the catheter.

Devices with catheter terminal baskets comprising single struts with electrodes are known as well from the prior art. Such a device may assure easier deployment and positioning against the target site. Because there are usually more electrodes placed on the catheter terminal, the ablation can be again either monopolar with an indifferent electrode, for example placed on the skin of the patient, or bipolar between particular electrodes on the catheter terminal. One disadvantage of this solution is limited struts, which means a limited number of electrodes creating a specific circular pattern in space. This disadvantage is caused by a need for mechanical stability of the particular struts to be able to keep a stable shape of the basket. This means to be rigid enough, the struts need to keep particular dimensions. The number of struts used is then limited by the size of the catheter. Another disadvantage of this solution is such a construction cannot fully assure a mutual distance of the struts in the deployed configuration, which means the distance between electrodes cannot be assured as well. That means the device may need to be repositioned multiple times in order to ensure proper ablation, which prolongs the duration of the procedure.

The quality and safety of the ablation needs to be increased on one hand, while risks for patients and duration of therapy need to be reduced on the other hand. There is thus a need for improved devices and methods of ablation, which would be more gentle and safer for the patient, with reduced complexity and with enhanced quality and reliability of the method and device itself.

SUMMARY OF THE INVENTION

Disclosed herein is a device and method of an ablation system, in particular an ablation method and device for pulsed field ablation by electric fields according to the description, which can address and solve the above-mentioned problems, and which would be more gentle and safer for the patient, with reduced time and technical complexity and with enhanced quality, efficacy and reliability of the system, method and device itself.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary aspect of the present disclosure is illustrated by way of example in the accompanying drawings in which like reference numbers indicate the same or similar elements and in which:

FIG. 1 is a block diagram of an exemplary ablation system.

FIG. 2 is an overview of an exemplary pulsed field ablation device with catheter.

FIG. 3A shows an exemplary catheter with a shaft assembly.

FIG. 3B is an exemplary representation of a cross-section of a shaft assembly.

FIG. 4 is an exemplary representation of a distal tip of the catheter with a basket assembly in expanded configuration.

FIG. 5 shows an exemplary distal tip of the catheter with a basket assembly in collapsed configuration.

FIG. 6A shows an exemplary expanded expandable basket.

FIG. 6B is a detail view of an exemplary expandable basket with filaments.

FIG. 6C is a detail view of an exemplary expandable basket with filaments and conductive wires.

FIG. 7A is a front view of an exemplary distal tip of a catheter.

FIG. 7B is a side view of an exemplary distal tip of a catheter.

FIG. 8 shows an exemplary braided mesh with elongated electrodes.

FIG. 9 shows an exemplary braided mesh with filaments and conductive wires inside of the lumen of the filaments.

FIG. 10 is an exemplary schematic view of a position of the basket assembly adjacent to a treatment site.

FIG. 11 is a schematic view of an exemplary mode of operation of electrodes.

FIG. 12 is a schematic view of another exemplary mode of operation of electrodes.

FIG. 13A is an example of a spatial pattern of electrodes on a distal tip of a catheter.

FIG. 13B is another example of a spatial pattern of electrodes on a distal tip of a catheter.

FIG. 14 is a view of a possible layout of electrodes already switched into a hybrid operation mode.

FIG. 15A shows an exemplary pattern of electrodes.

FIG. 15B shows another exemplary pattern of electrodes.

FIG. 15C shows another exemplary pattern of electrodes.

FIG. 16 shows a part of an exemplary pulsed field ablation protocol.

FIG. 17 a shows an example of inter-pulse pauses with voltage different than 0V.

FIG. 17 b shows examples of different biphasic pulses.

FIG. 18 is a view of one example of a terminal assembly.

FIG. 19 shows another view of an exemplary terminal assembly.

FIG. 20 shows an example of filaments joined together at their crossing point.

FIG. 21 is a view of a distal part of the basket assembly with merged structures and living hinges.

DETAILED DESCRIPTION

FIG. 1 shows an ablation system (100) for pulsed field ablation of a target tissue. The ablation system (100) described herein includes a pulsed field ablation device (101). The ablation system (100) may include or may be connected to other parts or devices appropriate for performing or for supporting during performance of a method of the pulsed field ablation described herein. The other parts or devices may be for example a control unit (111), a graphical user interface (GUI) unit (113), electrical control circuits (115), electrocardiogram (ECG) triggering circuits (117), an ECG recording device (129), ECG electrodes (125), a pacing device (131), catheter signal interconnection circuits (119) and/or an electro physiology (EP) display device (133), which may include an EP recording system. The EP display device may show and/or record data from one or more other devices connected to the ablation system (100). Further, the ablation system (100) may include a mapping device (135), for example three-dimensional (3D) mapping device or a real position measurement (RPM) device, and/or indifferent electrodes (127). The mapping device (135) records EGM (intracardial electrograms) for a place in a space measured for example by a catheter and creates a map of a heart's surface. It may also show a position and orientation of the catheter. Other possible methods for measurement of a catheter's real position may be via a sensor in a catheter (for example position measurement based on magnetics) or for example using impedance measurements on a catheter's electrodes or a measurement based on radiofrequency or a combination thereof. Advantageously, in some examples, the catheter used for the position measurements is the same catheter that is used for the ablation.

The pulsed field ablation device (101) includes a pulse generator (103) for generating short high voltage electrical pulses and a catheter (105) suitable for insertion into a cavity of a patient's body with a catheter distal tip (107) suitable for performing the pulsed field ablation of target tissue by pulsed electric fields with a set of electrodes (109). The catheter (105) being in electrical connection with the pulse generator (103).

The pulsed field ablation device (101) may include or may be connected to other parts or devices appropriate for performing or for supporting during performance of a method of pulsed field ablation described herein. The other parts or devices may be for example a remote control unit (111), a graphical user interface (GUI) unit (113), electrical control circuits (115), electrocardiogram (ECG) device including ECG triggering circuits (117), an ECG recording device (129), ECG electrodes (125), a pacing device (131), catheter signal interconnection circuits (119) and/or an electro physiology (EP) display device (133), which may include an EP recording system. The EP display device may show and/or record data from other devices connected to the ablation system (100). Further, the ablation system (100) may include a mapping device (135), for example a three-dimensional (3D) mapping device or a real position measurement (RPM) device, and/or indifferent electrodes (127). For example, the pulsed field ablation device (101) may be configured for use in or on a heart of the patient for example for the treatment of the heart tissue, for example for pulsed field ablation of the heart tissue, for example for pulsed field ablation of a myocardial tissue, for example for pulmonary vein isolation. Devices and methods disclosed herein may be used in other locations, for example all tubular tissues, organs or vessels in a body or for example tumor sites.

The catheter (105) shown in FIG. 2 includes a shaft assembly (201) and a catheter distal tip (107) located adjacent the distal portion of the catheter (105). The shaft assembly (201) defines a longitudinal central axis (203) of the catheter (105). The catheter (105) may further include a handle assembly (123) and a connection assembly (121). The catheter (105) may be steerable or non-steerable and can be introduced into its position for example via an introducer sheath (not shown) and with or without help of a guide-wire (not shown).

The connection assembly (121) of the catheter (105) may serve for interconnection of the catheter (105) with other parts of the ablation system (100). The connection assembly (121) may include a single connection portion or more spatially separated connection portions. The connection assembly (121) may be positioned at the proximal portion of the catheter (105) and/or for example may be a part of a handle assembly (123). The connection assembly (121) portion may include for example one or more electrical connections, mechanical connections, fluid connections and/or an input for a guide-wire.

The handle assembly (123) may be attached to the catheter shaft assembly (201) and may serve for example for steering and manipulation of the catheter (105), and/or for precise control of the movement and deflection of the catheter (105). In order to allow for the steering function, there may be knobs (not shown) connected to steering wires (not shown) that may be attached adjacent to the distal section of the catheter (105) fed through a separate lumen and connected to a knob or a steering mechanism (not shown) inside the handle assembly (123). The handle assembly (123) may further include the connection assembly (121) or one or more connection portions of the connection assembly (121), as well as other parts for example a grip (not shown) and/or a deployment mechanism (not shown) to deploy/retract the distal tip basket assembly (401, see FIG. 4 ) and/or expandable basket (409) by means of a push/pull of an inner elongated shaft (301) and/or an outer elongated shaft (303) relative to each other. The deployment mechanism may include for example an actuator for actuating the inner elongated shaft (301) against the outer elongated shaft (303) in a longitudinal direction.

FIG. 3A shows the catheter (105) with a shaft assembly (201). The shaft assembly may comprise an outer elongated shaft (303) and/or an inner elongated shaft (301). A cross section of an exemplary shaft assembly (201) in a section A-A shown in FIG. 3B, may include two concentric tubes, the outer tube being the outer elongated shaft (303), the inner tube being the inner elongated shaft (301). The shafts can translate relative to each other in a longitudinal direction along the longitudinal central axis (203). This translation can for example allow the deployment/retraction of the expandable basket (409) from a collapsed configuration to a fully expanded configuration and back.

The outer elongated shaft may comprise a proximal portion, a distal portion, and a body extending between a proximal and a distal end. The outer elongated shaft may be coupled to the handle assembly adjacent to its proximal portion and to the catheter distal tip adjacent to its distal portion.

The body of the outer elongated shaft (303) may include one or more lumens (309, 311), extending for instance along its entire length between the proximal and distal ends. The lumens may be for example adapted to lead wires or fluids, for example an irrigation fluid. One or more of the lumens may be configured to accept one or more of the inner elongated shafts. The body of the outer elongated shaft can be for example further defined by a proximal section (305) and a midsection (307). The midsection of the body may be designed with a flexible jacket compared to the proximal section to allow bending and increase flexibility of the outer elongated shaft. The proximal section for instance includes a stiffer material jacket to increase the torque and rigidity of the body of the outer elongated shaft. Suitable materials for construction of the jacket include, but are not limited to Nylon, TPU, HDPE or PEBA.

The body of the outer elongated shaft may include conductive wires. The conductive wires may lead through the outer elongated shaft's central lumen (309), or the outer elongated shaft may include several other lumens (311), hence one or more of the wires may lead through one or more of the other lumens (311). For example, the number of other lumens may match the number of filaments of a braided mesh on the catheter distal tip, for example if 20 filaments are used in the construction of the catheter distal tip, 20 other lumens may be used.

The conductive wires may extend from the basket assembly to the connection assembly for example adjacent to the handle assembly.

In some aspects, the inner elongated shaft may be configured to slide along the longitudinal central axis relative to the outer elongated shaft. Therefore, one or more of the lumens may for instance comprise a low friction liner, for example a polytetrafluoroethylene (PTFE) liner.

Rigidity and torque are important features that the outer elongated shaft should have, hence laterally above/around the PTFE liner the outer elongated shaft may include for example a braid of a metal or a rigid polymer wire wrapped around the inner layer of the body, which in some aspects is embedded within the outer jacket of the body, or may comprise a rigid polymer including but not limited to Polyimide, Polyamide, Polyether ether ketone (PEEK) or any other suitable material.

The outer layer of the outer elongated shaft may comprise a laminated polymer to provide a seamless, smooth and soft surface. Note that, as mentioned earlier, the outermost layers of the midsection and proximal section may be formed of different polymers, for example a nylon material could be used on the proximal section, while for example a PEBA, which is more flexible compared to nylon, could be used on the outermost layer of the midsection. Yet, both sections may have the same innermost layers. The outer elongated shaft may have a substantially constant outer diameter along its length.

The Outer Diameter (OD) dimension of the outer elongated shaft may for example fit the French catheter scale that is commonly used for catheter sizing standardization. The diameter in this scale is defined in Frenches (FR), where 1 mm=3 FR. The scale is usually from a 3 FR catheter up to a 34 FR catheter. For instance, the diameter of the outer elongated shaft may be between 5 FR to 20 FR, or from 7 FR to 16 FR, or from 9 FR to 15 FR. The diameter of the central lumen of the outer elongated shaft can be approximately between 0.1 mm and 5 mm, or 1 mm to 4 mm, or 2 mm to 3.5 mm, or 2.5 mm to 3 mm.

The inner elongated shaft may comprise a proximal end, a distal end, and a body extending between proximal and distal ends. The body of the inner elongated shaft may include one or more lumens (313), extending for example along an entire length between the proximal and the distal end of the inner elongated shaft or can have no lumen. The one or more lumens (313) of the inner elongated shaft may be for example designed to accommodate a standard guide-wire (not shown) and/or to lead a fluid, for example an irrigation fluid. The diameter of the one or more lumens (313) may be from 0.1 mm to 3 mm, or from 0.5 mm to 1.5 mm, or from 0.9 mm to 1 mm, or from 0.94 mm to 0.99 mm. One or more of the inner elongated shafts can be suitable for placing in the one or more lumens (309, 311) of the outer elongated shaft. Dimensions of the inner elongated shaft may be chosen to match the diameter of the designated lumen of the outer elongated shaft, but still the two structures need to allow their smooth relative translation. That means the outer dimensions of the inner elongated shaft (301) can be from 0.1 mm to 4.9 mm, or from 0.5 mm to 3.5 mm, or from 1 mm to 3 mm, or from 1.28 mm to 2.8 mm.

Since the inner elongated shaft can be suitable for accommodation of a guide-wire inside its lumen, a low friction liner, for example a PTFE liner, of the inner lumen can be used.

As mentioned above, the inner elongated shaft can be translated relative to the outer elongated shaft to deploy the basket assembly/expandable basket, hence for instance a braided socket is weaved along the length of the PTFE liner creating a body of the inner elongated shaft. Another aspect may include a cut hypotube instead of a braid in a body of the inner elongated shaft to improve its flexibility and torque.

Laterally above the layer with the braid or the hypotube, a polymer jacket can be melted/laminated to enhance the softness of the tube and provide a seamless surface. A variety of polymers could be used for the jacket, exemplary materials may be NYLON, polyether block amide (PEBA), Polyether ether ketone (PEEK) or Polyimide.

The distal tip (107) of the catheter of the example shown in FIG. 4 . further includes a basket assembly (401). The basket assembly (401) may comprise a basket assembly proximal portion (403), a basket assembly distal portion (405) and a basket assembly body (407) extending between the proximal and distal portions. The basket assembly body may include a central body portion (419) spreading around the plane (425) intersecting the basket assembly in a portion with a highest diameter (in one of its expanded configurations) in proximal and distal directions, occupying about ⅓ of the basket assembly body. The basket assembly body may further include a distal body portion (421) extending distally from the central body portion (419) and proximal body portion (423) extending proximally from the central body portion (419), each of them occupying about ⅓ of the basket assembly body (407).

The basket assembly (401) comprises an expandable basket (409). The basket assembly proximal portion (403) may include an attachment of the proximal portion of the expandable basket (409) adjacent to the distal end of the outer elongated shaft (303). The distal portion of the basket assembly (401) may include an attachment of the distal portion of the expandable basket (409) adjacent to the distal end of the one or more of the inner elongated shafts (301) creating a terminal assembly (411).

The terminal assembly (411) may be advantageously designed without, or at least with reduced structures protruding in the distal direction from the basket assembly distal portion (405), for example a cap or similar formation. This is especially advantageous in situations where at least part of the ablation method needs to be performed on a relatively flat treatment site.

An exemplary solution of terminal assembly may be an overmolded structure. Filaments may be fixed to each other and/or to distal end of the inner elongated shaft by an overmolding process, creating an overmolded terminal assembly. Another fixation procedure (and/or terminal assembly creating procedure) similar to overmolding may be for example tipping, where the filaments are at least partially melted and pressed into a pre-shaped mold and so connected together and/or to the inner elongated shaft. A lamination is another example process to fix the filaments at their distal ends to create a terminal assembly. The terminal assembly may be created by swaging or crimping of a filament's distal ends as well. The filaments may be brought together at the terminal assembly area and swaged or crimped together by for example some kind of metal ring.

In another example a terminal assembly may be created as a hinged mechanical structure as shown in FIG. 18 . For example, one or more filaments may be at their distal end in the area of terminal assembly fixed to articulated elements (1801), which comprise for example lateral narrow portion (1803) and distal portion (1805) which is wider than lateral narrow portion (1803). The lateral narrow portion (1803) may be for example in a form of pin with square, rectangular, circular, oval or other suitable cross section. The distal portion (1805) may have for example a form of an oval or a circle or in another example of ball or sphere. Other possible shapes of the distal portion (1805) could be cylinder, cone, cube or block. It may have one of the dimensions the same as the lateral narrow portion (1803), for example in case the whole articulated element (1801) is made out of one piece of sheet-like material (metal sheet, polymer sheet) or not (for example in case the articulated element is casted or forged. The articulated element (1801) may be for example made of metal (for example nitinol) or other material for example polymer or thermoplastic. The fixation of filaments to the articulated elements may be done for example by welding, gluing or crimping. An area of the connection (1807) may be for example at least partially laminated to prevent possible tissue damage and to seal the assembly. The articulated elements are then fixed in a central bullet structure (1809). This may be for example a hollow structure with cut windows (1811) suitable for accommodation of the proximal part (1803) of the articulated elements (1801). The distal parts (1805) of the articulated elements are in this case placed in the cavity (1813) inside the hollow structure. The distal parts (1805) of the articulated elements may in some examples have dimensions (cross section or width) bigger than dimensions of windows (1811). This prevents slipping of the distal parts (1805) of the articulated elements (1801) through the windows (1811) thus holding articulated elements, and together with them the connection area (1807) and distal parts of the filaments attached to the central bullet structure (1809). The central bullet structure (1809) may comprise several parts connected together (for example by welding, gluing or other mechanical means like snaps, threading, screws, bolts . . . ). It may have different outer shapes as well, for example a cylindrical, spherical or oval. The shape of the cavity (1813) may correspond to the outer shape or may differ. The central bullet structure may include fixation part (1815) for fixation of a distal end of an inner elongated shaft to the central bullet structure. The fixation part (1815) may have for example a shape of a hollow tube connected to the central bullet structure. The fixation part is suitable for accommodation and/or connection of a distal part of the inner elongated shaft and may allow for a flow and/or redirection of a fluid, for example an irrigation fluid coming out of a lumen of the inner elongated shaft. The fixation part may interfere or may be in mechanical and/or fluid connection with the cavity (1813). It may be adapted to direct at least part of the irrigation fluid into the cavity of a central bullet structure for example by apertures (1901) as shown in FIG. 19 .

Such a hinge mechanical structure as described above may allow for easier radial movement (regarding longitudinal central axis of the catheter) of the filaments in the area of terminal assembly, which may be advantageous during manipulation with an expandable basket, particularly with transition (deployment/retraction) between a collapsed configuration and one or more expanded configurations.

In case metal parts are used in the design of a terminal assembly, they may be for example used as electrodes, either for ablation or for sensing or mapping or combination of thereof.

The expandable basket may be attached to the inner elongated shaft and/or to the outer elongated shaft for example by gluing, welding, lamination or by mechanical means.

The expandable basket (409) is for instance configured for transition (deployment/retraction) between a collapsed configuration, shown in FIG. 5 , and one or more expanded configurations. The transition (deployment/retraction) can be caused by a pre-tension shape of the braided mesh (413) and/or filaments (415) and/or by a linear displacement of the inner elongated shaft (301) against the outer elongated shaft (303) along a longitudinal central axis (203) of the catheter (105) or by combinations thereof. Another possibility for deployment/retraction of the expandable basket (409) may be by a tension of an additional supportive structure for example an inner coil or balloon (not shown).

The expandable basket comprises filaments braided into a mesh. In the collapsed configuration, the cross-section of the expandable basket may be equal or dimensionally close to the cross-section of the outer elongated shaft, though in one aspect the cross-section of the expandable basket may be smaller than the cross-section of the outer elongated shaft and may depend on the dimensions of the outer elongated shaft. In the expanded configuration the cross-section of the expandable basket may be significantly larger than the cross-section of the outer elongated shaft. Fully expanded expandable basket may have a maximum cross-sectional diameter of, for example, from 20 mm to 40 mm or from 22 mm to 38 mm or from 25 mm to 35 mm. Such dimensions of a fully expanded expandable basket may be suitable for example for placement in heart cavities. For larger body cavities, for example, the expandable basket may have larger dimensions, e.g. from 30 mm to 150 mm, or from 40 mm to 120 mm, or from 50 mm to 100 mm. In other situations, a fully expanded expandable basket having smaller dimensions may be suitable for smaller body cavities. Such a smaller expandable basket may have dimensions in its fully expanded state for example from 3 mm to 25 mm, or from 5 mm to 15 mm, or from 7 mm to 10 mm.

In some aspects, the filaments (415) braided into the braided mesh (413) are not cut adjacent to the distal portion of the expandable basket (409), but the filaments (415) may rather be bent at the distal portion and attached adjacent to the distal portion of the inner elongated shaft creating a terminal assembly. The bent filaments may then be directed back to the expandable basket (409) or the outer elongated shaft, where they can be terminated. FIG. 6A shows the expandable basket (409) in greater detail with bent filaments in its distal portion (603).

The expandable basket made out of the braided mesh has advantages over a prior art solution with unbraided struts, in that the expandable basket has higher mechanical stability even while using comparably thinner filaments. More filaments in the structure may also allow more electrodes to be used. The electrodes placed on the filaments can also be distributed more optimally, which means for example they can be placed closer together or can create a desirable pattern on the expandable basket. Another advantage of the expandable basket made of the braided mesh is the higher mechanical stability of the structure that can ensure stable and predictable distances between electrodes.

The braided mesh may be heat-treated which may ensure deformations and fixation of such deformations of the filaments. Such deformed filaments then ensure that during expansion and collapse of the basket assembly (expandable basket) the crossing points of the filaments (points, where the filaments intersect each other) stays relatively stable regarding a filament length. It means the filament crossing points stay at the relatively same filament length distances in the collapsed state as well as in all expanded states of the basket assembly (expandable basket). What is changing is a mutual angle of the particular filaments creating the crossing points (for example from about 2 degrees up to 178 degrees or vice versa). Some kind of minor lengthwise movement of the crossing points may not be completely avoided by this process, however it stays in limits where it doesn't compromise dimensional and/or mechanical stability of the braided mesh. This feature may then for example allow placement of the electrodes in the crossing points of the filaments and/or ensure stabile, predictable desired mutual positions of electrodes and/or their mutual distances.

Even further structure stability of the expandable basket, made out of the braided mesh, may be achieved for example by joining of the particular filaments (included in the braided mesh) together. The filaments may be for example joined together at their mutual crossing points. An exemplary solution may be seen in FIG. 20 . The joints (2001) may be fixed (not allowing any mutual movement of the filaments in the joining point) or interacting (some kind of mutual movement of the filaments in the joining point is possible). The joining may be achieved for example by gluing, welding, lamination, bonding, tying (for example with some kind of string) or melting. Another option could be tying the filaments together for example by a ring structure or by crimping. In case the ring structure is made out of conducting material (for example metal), it can serve also as an electrode. The same is true for the crimping. The metal connector may serve as an electrode as well.

Particular meshes within the braided mesh do not need have to have uniform size, on the contrary, the sizes of particular meshes may differ. The sizes may for example increase from the distal portion and the proximal portion of the expandable basket (where they may be smallest) in the direction toward the middle part of the expandable basket, where they may be the largest. In other words, the dimensions of the meshes in the central body portion of the basket assembly may be larger than the dimensions of meshes in the proximal and distal body portions of the basket assembly. The dimensions may for example increase linearly or exponentially. The circumference of the meshes in the proximal and distal body portions may be for example between 1 mm to 40 mm, while the circumference of the meshes in the central body portion may be for example between 5 mm to 80 mm. The number of rows of the meshes, creating a complete braided mesh of the expandable basket may be between 4 to 40.

Two or more filaments creating a braided mesh and hence expandable basket may be merged or joined together at their proximal and/or distal ends to create a merged structure (2101) in the proximal and/or distal portion of the expandable basket as shown schematically in FIG. 21 . Such a solution may reduce a number of filaments at the proximal and/or distal portion of the expandable basket. Lowering a number of filaments entering related structures like the basket assembly proximal portion which may include an attachment of the proximal portion of the expandable basket adjacent to the distal end of the outer elongated shaft, and/or the distal portion of the basket assembly which may include a terminal assembly may reduce a complexity and/or enhance mechanical stability of those structures hence of the whole basket assembly. It may even help to reduce risk of an ablation procedure, due to a reduction of the number of members in the structures with reduced number of filaments. In terms of the filament length the merged structure in proximal or distal part of the filament may occupy from 1% to 30% or from 3% to 20% or from 5% to 15% of the total length of the filament included in the expandable basket. As stated before, the filaments may be merged in distal or proximal ends of the filaments or in both. In the case where the filaments are merged in both ends, the merged length may be the same on both ends, or it may differ. Relative to the length of the expandable basket in its collapsed configuration, the merged part of the filaments, either on proximal or distal end of the basket, may occupy from 1% to 35% or from 4% to 25% or from 6% to 20% of the length of the collapsed basket. The filaments may be merged for example by gluing, welding, lamination, bonding, tying or melting. Another option could be joining the filaments together for example by some kind of tubular structure or by crimping. The tubular structure may be for example a tube made of metal or polymer or thermoplastic with lumen. In this case the end parts of the filaments would be put through the lumen of the tube, fixed there (for example by gluing, welding, lamination, bonding, tying, melting or swaging) and so joined together. Another option could be usage of a multi-lumen tube, made of metal or polymer or thermoplastic, where each end part of each filament to be joined would be put through a separate (its own) lumen of the multi-lumen tube, fixed there (for example by gluing, welding, lamination, bonding, tying, melting or swaging) and so joined together.

The diameter of the filaments in the braided mesh may be from 0.2 mm to 1 mm or from 0.4 mm to 0.8 mm or from 0.5 mm to 0.7 mm. The number of the filaments braided into the braided mesh creating an expandable basket can vary from 5 to 150 or from 10 to 60 or from 15 to 50 or from 16 to 32.

The filaments may be made out of electrically insulating, nonconductive material, for example polymers or thermoplastic elastomers like Nylon, Fluorinated ethylene propylene (FEP), Polyethylene (PE), PEBA, PEEK, Polyimide (PI), Polypropylene (PP), PTFE, Polyurethane (PU), Polyethylene terephthalate (PET) or for example Silicon. The material may be further reinforced for example by glass fibers. The cross-section of the filament may be circular, or alternatively other cross-section shapes are possible, for example but not limited to oval, round, semicircular, rectangular, square, flat, or star-shaped. The filaments (415) may be for instance formed of tubes with at least partially hollow structures with lumen (601) as can be seen on FIG. 6B. Some or all of the filaments (415) can be hollow along their entire length or for example the lumen (601) may be present only in a portion of the length of one or more filaments (415). Another aspect may include a braided mesh (413) comprising a first subset of the filaments (415) including lumens (601) and another subset of the filaments (415) without lumens, or all of the filaments may be without lumen.

There are further options to enhance a mechanical stability of the filaments. A use of a multilayer wall may be one of them. The wall of the filament may include for example more than one layer of material. Materials of different properties may be used, which in combination may result in more mechanically stable wall thus more mechanically stable filament. Such a combination may use layers made each one from different material from a group of polymers or thermoplastics, for example from Nylon, Fluorinated ethylene propylene (FEP), Polyethylene (PE), PEBA, PEEK, Polyimide (PI), Polypropylene (PP), PTFE, Polyurethane (PU), Polyethylene terephthalate (PET) or for example Silicon. Another possible option may be usage of layers from the same kind of material, but different subgroups of the materials with different properties for each layer. Materials used in the particular layers may be further reinforced for example by glass fibers.

In another aspect, the filaments may be for example further mechanically reinforced by insertion of a mechanical support into a lumen of a filament. Such a mechanical support may be for example in form of struts placed in the filament lumen. The struts may be placed into the full length of the filament, or in a full length of filament lumen, in the case that the filament does not have a lumen in its entire length. Another possible option would be to place the struts into only a portion of length of the lumen, thus leaving part of the filament reinforced with a strut and another part without a strut reinforcement. The struts may be for example made of nitinol, for example with electrical insulation layer, for example from Polyamide (PA), Polyimide (PI) or PTFE. Other possible materials suitable for struts may be polymers or thermoplastics, for example from Nylon, Fluorinated ethylene propylene (FEP), Polyethylene (PE), PEBA, PEEK, Polyimide (PI), Polypropylene (PP), PTFE, Polyurethane (PU), Polyethylene terephthalate (PET) or for example Silicon.

Yet another option suitable for further reinforcement of the filaments is to fill at least part of the lumen of the filament by glue or melted polymer or thermoplastic material.

A braided mesh then may be constructed in a way that all of the filaments included in the mesh may be reinforced or only a portion of the filaments included in the mesh may comprise a reinforcement and another portion of the filaments may be without it.

At least one of the filaments creating a braided mesh may include at least one place where the structure of the filament is locally mechanically weaker than rest of the filament. Such a place may create so called living hinge (2103), schematically shown in FIG. 21 . The living hinges may be useful for defining more or less exact places, where filaments included in the braided mesh, and hence in the expandable basket bend easier and where the bends on the filaments create smaller radiuses (or directly kinks) in comparison with filaments without such a living hinge. This may further help in defining a more predictable shape of the deployed expandable basket in at least one of its deployed positions. Establishment of such a living hinge on the filament may include thinning or cutting of part of the filament. Thinning may be done for example by squeezing or thermoforming of a particular place of the filament. The thinning may be made around whole circumference of the filament, or only partially. Partial asymmetrical thinning may be advantageous, since such created hinge may define a particular direction in which the filament bends easier compared to other directions. In one example of the expandable basket, the living hinges created on the filaments may allow easier bending of the filaments, and hence the braided mesh, for example in a radial direction from longitudinal central axis of the catheter. For example living hinges creating smaller radiuses or kinks on the filaments in a distal body portion (421) of the basket assembly body or in an area of terminal assembly may help in the shaping of the expandable basket (basket assembly body) in an area located distally from a plane intersecting the basket assembly at the portion with the highest diameter (in one of its expanded configurations) in a way such that at least some of the distal part of the basket (in an area of a distal body portion) may form larger angles (radially from elongated axis) compared to a proximal part of the basket (in an area of a proximal body portion). In extreme cases the distal part of the basket (in an area of a distal body portion) may form an angle of 90° or more (radially from elongated axis) to achieve an expanded state where at least part of the expandable basket including electrodes becomes longitudinally the most distal part of the catheter, without any other part protruding more distally (for example terminal assembly). Such a configuration may be advantageous for example in an ablation of a relatively flat treatment site.

At least one living hinge as described in previous paragraph may be included on at least one part of the braided mesh, where the filaments are merged together (on a merged structure). In this case the living hinge is a place on the merged structure, which is locally mechanically weaker then rest of the merged structure and may be created by thinning or cutting of the merged structure for example after merging. Another option to establish a living hinge on the merged structure, particularly in the case where the merged structure includes polymer tube and where the filaments are merged in the lumen of the tube or in the multiple lumens of multi-lumen tube, is to pre-thin or pre-cut the polymer tube before inserting the filaments. Such a pre-thinning of the tube may be done for example by squeezing, thermoforming or by molding, for example injection molding.

The living hinges may be created in an area of a distal body portion, central body portion and/or proximal body portion of the basket assembly body. They may be placed for example in a proximal area from 0% to 20% or 0% to 15% or 0% to 10% of the length of the collapsed basket in a case where they are in an area of a proximal body portion. They may be placed in a distal area from 0% to 20% or 0% to 15% or 0% to 10% of the length of the collapsed basket in a case where they are in an area of a distal body portion. They may be part of the terminal assembly as well. In a case where they are placed in the central body portion, the hinges may be placed on a plane intersecting the basket assembly in a portion with a highest diameter or from −20% to +20% or from −10% to +10% or from −5% to +5% distally from this plane or from the center of the collapsed basket.

The expandable basket may include one or more electrodes or a set of electrodes. The electrodes can be configured for at least one of generating an electric field for ablating tissue, or obtaining or sending electrical or other signals, for example signals for tissue mapping, ECG monitoring, impedance measurement and/or detection of contact with a tissue. Another function of the electrodes may be serving as markers for an X-ray. The electrodes may be coupled to particular filaments of the expandable basket. Electrodes can be placed on each of the filaments or only on some of the filaments. Each filament comprising the electrode may include one or more of the electrodes, for example from 1 to 15, or from 1 to 10, or from 1 to 6, or from 1 to 3 electrodes. The electrodes can be of one type or of different types. The overall number of electrodes placed on the expandable basket may be from 1 to 200, or from 5 to 100, or from 10 to 50, or from 15 to 40, or from 20 to 35. Spatial distances between electrodes in the fully expanded configuration of the expandable basket may be from 0.1 mm to 15 mm, or from 0.5 mm to 10 mm, or from 1 mm to 6 mm, or from 2 mm to 4 mm.

In an example, the electrodes may be placed in areas where the filaments cross each other (filaments crossing points). Such a position may be advantageous due to the ability to keep a more stable distance between electrodes during different configurations of an expandable basket and such a configuration may also advantageously prevent unwanted contact between electrodes, especially in cases where the expandable basket is not in a fully expanded configuration.

Each filament may also include electrodes of one type or different types, or different filaments can accommodate different types of electrodes. Different types of electrodes may be understood as electrodes with different functions, for example ablation electrodes, measurement electrodes and so on, or physically different electrodes with for example different shape, size, design, materials and so on, or a combination of types of electrodes with different functionality and physical properties. For example, in configurations with ring-shaped electrodes placed on the filaments, all electrodes may have the same diameter and may differ in length, so there may be for example two or more groups of such electrodes, each group having different length. A number of electrodes in each of the groups may be the same or may differ. In an extreme example, each electrode on the expandable basket may have a different length. In configurations with ring-shaped electrodes, such electrodes may have a diameter between 0.2 mm to 3 mm, or from 0.4 mm to 2 mm, or from 0.5 mm to 1 mm, and may have a length between 0.1 mm to 10 mm, or from 0.2 mm to 8 mm, or from 0.3 mm to 6 mm, or from 0.4 mm to 4 mm.

In one example there may be a first group of 5 to 20 shorter electrodes, with lengths of for example 0.3 mm to 3 mm, and a second group of 5 to 30 electrodes which may be longer, for example with lengths from 0.6 mm to 4 mm. Advantageously the electrodes from the first group may be used for at least one type of measurement, for example for measurement of an intracardial ECG (EGM), or an ablation, and the electrodes from the second group may be used for an ablation, either independently or in combination with the electrodes from the first group.

The electrodes can be placed on the body of the basket assembly. For example, the electrodes may be placed on the central or distal body portion, in some cases the electrodes may be even placed on the proximal body portion. Other electrodes may be placed on or in an outer elongated shaft, inner elongated shaft, catheter distal tip or terminal assembly. In configurations where the electrodes are placed on the elongated shafts, distal tip or a terminal assembly and where ring-shaped electrodes are used, then they may have a diameter of 0.2 mm to 10 mm, or from 0.5 mm to 8 mm, or from 1 mm to 6 mm, or from 2 mm to 5 mm and may have a length between 0.1 mm to 20 mm, or from 0.2 mm to 15 mm, or from 0.3 mm to 12 mm, or from 0.4 mm to 10 mm.

The layout of the electrodes on the expandable basket may ensure continual, for example circular ablation areas while the expandable basket is in the expanded position and may create a pattern.

For instance, the layout of the electrodes on the expandable basket may ensure continual, circular ablation areas even while the expandable basket is held in various expanded positions between a fully collapsed and a fully expanded position and may create a pattern as well.

Additional electrodes, for example the ones placed on or in an outer elongated shaft, inner elongated shaft, catheter distal tip or terminal assembly may be part of the pattern or may be operated independently to other electrodes. For example, electrodes at the area of catheter distal tip or terminal assembly may be used for point-like ablation. There may be special dedicated electrodes at the area of distal tip or terminal assembly or for example metal parts of the terminal assembly may serve as an electrode, or combination of thereof may possible.

The pattern (701) created by the electrodes (109) may be for example a circular pattern in space around the longitudinal central axis (203) at least when the expandable basket (409) is in one of its expanded configurations as can be seen in FIG. 7A. Other two dimensional or three-dimensional patterns created by the electrodes (109) are possible. The patterns (701) may be centered around the longitudinal central axis (203) or not. The patterns (701) may have different shapes, including but not limited to circular, ellipsoidal, square, rectangle, polygonal, planar or other or the placement of the electrodes (109) on the expandable basket can be irregular. There can be for example one pattern (701) in one plane or more patterns (701) in one plane or more patterns (701) in different planes.

Patterns created by the electrodes may be positioned on the basket assembly body, particularly on the distal body portion, central body portion or proximal body portion as shown in FIG. 7B. Patterns may even extend into more than one of these portions. For example, for a treatment of a flat treatment site positioned distally from the basket assembly, the pattern of electrodes may be positioned advantageously on the basket assembly distal portion. Particularly the pattern may be positioned in a section of the basket assembly bounded by an area making an angle (703) of 0° to 90° to the central axis (203) in a center of a plane (425) intersecting the basket assembly in a portion with a highest diameter (in one of its expanded configurations). In some configurations, a pattern may be positioned partially on the basket assembly body distal portion and partially on the basket assembly body central portion. In some configurations, a pattern may be positioned in a section of the basket assembly bounded by an area making an angle (705) of 0° to 120° to the central axis (203) in a center of a plane (425). Such placement of the pattern may be particularly advantageous for treatment of a vessel orifice, for example an orifice of a pulmonary vein. In situations where the treatment site has a tubular shape, the pattern may be placed on the basket assembly middle portion, particularly in a section of the basket assembly bounded by areas making an angle (707) of 45° to 135° to the central axis (203) in a center of a plane (425). If a flat treatment site is positioned proximally from the basket assembly, for example a septum, the pattern of electrodes may be positioned on the basket assembly proximal body portion or partially on the proximal body portion and partially on the central body portion, particularly in a section of the basket assembly bounded by areas making an angle (709) of 90° to 180° to the central axis (203) in a center of a plane (425). Optionally electrodes may be placed in all portions of the basket assembly, thus creating patterns in all of the portions and only patterns necessary or optimal for performing a particular therapy may be chosen to perform the therapy.

Particular patterns may be created by all electrodes placed on the expandable basket or with just a portion of the electrodes. The patterns may have different numbers of electrodes in various expanded positions between fully collapsed and fully expanded positions of the expandable basket. The neighboring electrodes in the pattern may have distances between each other for example 0.1 mm-15 mm, or 0.5 mm-10 mm, or 1 mm-6 mm or 2 mm-4 mm.

Electrodes are for example electrically connected to the pulse generator, for example with conductive wires. The electrodes may be electrically or communicatively connected to other units or parts of the pulsed field ablation device as well as for example with the mapping device, EP display device, pacing device, ECG recording device, catheter signal interconnection circuits, ECG triggering circuits, electrical control circuits, GUI unit or remote control unit. Apart from the ring-shaped electrodes mentioned before, the electrodes may have any of many different shapes, for example tubes threaded around the filaments, coiled metal sheets, square and/or rectangle or other shapes of conductive materials attached to the filaments. Other possible forms of electrodes (109) may be elongated continuous electrodes drawn along the surface of a portion of the filament (415) in a way they do not touch at crossing points of the filaments (415) in the braided mesh (413) as shown in FIG. 8 . The electrodes (109) may be attached on the particular filaments (415) of the expandable basket by any means, for example by way of mechanical attachment, swagging, crimping, gluing, lamination, deposition and/or soldering. The electrodes may be made out of any electrically conductive material for example copper, gold, steel, titanium, platinum, platinum-iridium, and so on. In a case where there is at least one filament made out of conducting material, it could serve as an electrode as well. In a case where the whole conducting filament is uninsulated the whole filament may serve as an electrode, in case the filament is for example partially electrically insulated, the bare, uninsulated portion may serve as an electrode.

Conductive wires may provide an electrical connection between the electrodes and a pulse generator. The conductive wires may be a part of a structure of the basket assembly (401). For instance, the conductive wires (417) may be positioned at least partially in the lumen (601) of the filaments (415) as shown in FIG. 6C or in FIG. 9 . There can be one or more conductive wires (417) coupled to each of the electrodes, or one or more electrodes can be coupled to a single leading wire. The conductive wires (417) may be incorporated into the one of the walls of the shaft assembly, for example into the wall of the outer elongated shaft. The conductive wires can also be positioned in the central lumen of the outer elongated shaft or there can be separate lumens in the outer elongated shaft suitable for the placement of conductive wires. The conductive wires may be terminated adjacent to the electrodes or may lead spatially further along the length of the filament past the electrode. The conductive wires may for example be positioned along the whole length of the filaments of the basket assembly. Optionally some of the conductive wires (417) may be terminated adjacent to the electrodes while others may lead spatially further along the filaments past the electrode or may be positioned along the whole length of the filaments of the basket assembly.

In a case where the conductive wires are positioned along the whole length of the filament, the design solution of the expandable basket, where the filaments are bent and returned to the expandable basket, rather than cut, at the expendable basket's distal end is particularly advantageous. Because the particular conductive wires are configured to carry electrical pulses between electrodes and the pulse generator, an insulation of the cut filaments with the conductive wires inside would be extremely challenging at the terminal assembly. On the other hand, in examples comprising bent filaments with conductive wires inside, the insulation of the terminal assembly can be easily assured.

The material used for conductive wires may be any electrically conductive material for example copper, stainless steel, steel, nitinol, aluminum, gold, platinum, silver and so on. The conductive wires may be insulated or uninsulated. The wires may be insulated using any suitable material, for example polyimide, polyurethane, polyester, polyvinylchloride (PVC), rubber, rubber-like polymers, nylon, polyethylene, polypropylene, silicone, fiberglass, ethylene propylene diene monomer (EPDM), different fluoropolymers like polytetrafluoroethylene (PTFE) and so on. The wires may be made of a single conductor or with a group of conductors, whereas a wire made of a group of conductors is sometimes called “cable”. In case the wires are insulated a minimum breakdown voltage of the wire insulation should be at least 100V, or 500V, or 1000V or 4000V or 10000V. The diameter of the wires with insulation may be limited by the dimensions of other structures of the device such as for example the filaments and a minimum voltage it has to be able to carry without risk of breakdown. Typical diameter of the wires with or without insulation may be between 0.05 mm and 0.7 mm, or between 0.07 mm and 0.5 mm, or 0.1 mm to 0.3 mm or between 0.11 mm to 0.2 mm or between 0.12 mm to 0.18 mm.

The construction of the braided mesh out of electrically insulating material as described with one or more conductive wires inside hollow filaments may be particularly advantageous for an ablation system based on the principle of pulsed field ablation by pulsed electric fields. The pulsed field ablation method as described further, requires electric fields generated around electrodes. To generate the fields, electrical pulses have to be carried by particular conductive wires between the electrodes and the pulse generator. When the filaments are electrically nonconductive, and the conductive wires are kept inside the filaments as described herein, the electrical insulation of the particular conductive wires can be ensured even at voltage levels of several kV, for example from 1 kV to 10 kV, carried by the conductive wires. However, an option of braided mesh with at least one or more filaments made out electric conducting material (for example nitinol, copper, stainless steel, steel, aluminum, gold, platinum or silver) may be possible as well. Such conducting filaments may be insulated or not or only partially. They not only that could possibly lead electrical current, but could act as an electrode (when uninsulated or insulated only partially) and/or as a further mechanical support of the braided mesh hence the expandable basket.

Another advantage of a braided mesh made of polymer or thermoplastic elastomer filaments is the ease of manufacturing compared for example to a metallic braided mesh. The braided mesh may be for example made with the help of a three-dimensional mandrel device. The particular filaments creating the mesh may be placed over the mandrel in a desired pattern. The filaments may already include the conductive wires. The whole structure may then be heated up, for example close to the melting point of a material of the filaments and after that the structure may rapidly be cooled down. The filaments made of thermoplastic elastomer or polymers generally require lower temperatures to reach the melting point over most metals, so the manufacturing process can be faster, more efficient and can demand less energy input. Another advantage of such a manufacturing process is the conductive wires do not need to be heated to extreme temperatures, to a degree where the electrical properties of the wire may be compromised. This situation can happen, for example when the braided mesh is made of the metallic wires, where the mesh wires also serve as the electrically conductive wires.

The braided mesh with inserted conductive wires may be attached to the outer elongated shaft and inner elongated shaft creating an expandable basket and part of the basket assembly. The electrodes may be attached at the particular filaments of the braided mesh before or after the attachment of the braided mesh to the elongated shafts. The pulse generator is a part providing generation of electric signals for catheter electrodes. The pulse generator may allow settings for example of an amplitude, a shape of the electrical pulse and/or a number of pulses during activation. The pulse generator may diagnose electrical waveforms to measure power as well. The pulse generator may enable synchronous operation with an ECG device or another part of the ablation system or device.

Further, a method of ablation with the described pulsed field ablation device is disclosed.

One method comprises the step of disposing a catheter (105) adjacent to the treatment site, for example a cardiac chamber, in the patient via a blood vessel. The catheter (105) may be inserted into the blood vessel of the patient percutaneously.

Other support structures and/or devices may be used to help navigate the distal tip of the catheter to its desired location. Examples of such devices include a guide-wire or a sheath. The catheter distal tip may be delivered proximally to the treatment site in a collapsed state, for example through a sheath. In the collapsed state the diameter of the basket assembly at the catheter distal tip may be less than or approximately equivalent to the diameter of the outer elongated shaft of the catheter. Such a configuration allows easy access of the catheter distal tip proximal to the treatment site.

The treatment site may be for example located inside the body, for example in or on a heart, for example in a heart cavity, particularly for example in a left atrium of the heart. The treatment site may for example include a pulmonary vein orifice. Other locations of the treatment site may be for example all tubular tissues, organs or vessels in a body or for example tumor sites.

When the catheter distal tip is delivered to the treatment site, the basket assembly of the catheter is deployed from the collapsed or semi-collapsed configuration to one of the expanded configurations. This deployment may be caused by a pre-tension shape of the braided mesh or its filaments or by a linear displacement of the inner elongated shaft against the outer elongated shaft along a longitudinal central axis of the catheter, by a tension of an additional supportive structure for example an inner coil or balloon (not shown), or by a combination of thereof.

The catheter distal tip (107) may then be placed adjacent to a target tissue of the treatment site (1001), for instance at least part of the basket assembly (401), and/or part of the expandable basket (409) is brought in contact with the treatment site (1001). In this position at least a portion of the set of electrodes (109), placed on the basket assembly (401) may be in contact with the tissue of the treatment site (1001). A schematic of an example position can be seen in FIG. 10 . The terminal assembly (411) may improve contact of the electrodes with the treatment site by its flat design without distally protruding structures. When there are no distally protruding formations on the basket assembly (401), especially on the basket assembly distal portion (405), it is easier to get the electrodes in contact with the treatment site even in situations where the treatment site is relatively flat.

After positioning the catheter distal tip adjacent to the treatment site an optional step of measurement can be carried out with or without the catheter. Different kinds of measurements can be performed with the goal of, for example, diagnostics of type or quality of a tissue at or around the treatment site, spatial position of the catheter distal tip, particularly for example the spatial position of the catheter distal tip against the treatment site, contact of the catheter distal tip and/or particular electrodes with the target tissue of the treatment site or with a goal of understanding electrophysiological processes of a tissue adjacent to the electrodes. For example, the electrodes may be used for a measurement of contact with a target tissue as well and may be placed on the expandable basket, for example on the filaments of the braided mesh. The measurement electrodes may be different electrodes than the ablation electrodes or the ablation electrodes may be used for the measurements. It is possible to combine separate measurement electrodes with the ablation electrodes with measurement functions on one catheter distal tip as well. A separate measurement device may be used to carry out the measurement step, for example a separate measurement catheter (not shown), an ECG device including ECG triggering circuits, an ECG recording device, ECG electrodes, an intracardial ECG (EGM), an intracardial echo device, an esophagus temperature measurement device, a fluoroscopy device, RTG device, MR device, and so on. The measurement step may be carried out once or may be repeated several times during an ablation procedure.

The ablation of the target tissue of the treatment site (1001) for instance uses a principle of pulsed field ablation caused by pulsed electric fields of proper parameters. Although the terms “electric fields” or “pulsed electric fields” are mentioned here, electric fields as contemplated herein may further comprise a magnetic component.

The procedure of basket assembly deployment, measurements and ablation can be carried out in several stages. For example, the expandable basket may be delivered adjacent to the treatment site in a fully collapsed configuration. After delivery it can be deployed to its first expanded configuration. For example, the pre-tension shape of the braided mesh and/or filaments may cause this first transition. In this configuration for example further manipulation with the basket assembly can be carried out as well as measurements and/or ablation. Further repositioning, measurement and/or ablation can be carried out in this position in any order as well.

Then the basket assembly may be deployed into a second expanded configuration. The second expanded configuration can be achieved for example by a linear displacement of the inner elongated shaft against the outer elongated shaft along a longitudinal central axis of the catheter. In this configuration for example further manipulation of the basket assembly can be carried out as well as measurements and/or ablation. Further repositioning, measurement, and/or ablation can be carried out in this position in any order as well.

The basket assembly can be for example deployed into several different expanded positions, during which further repositioning, measurement and/or ablation can be carried out.

In the case of pulmonary vein isolation ablation the set of electrodes may create a circular shape around the pulmonary vein orifice. After the ablation the shape of the ablated tissue may have a circular shape around the pulmonary vein orifice as well. Several such shapes of ablated tissue may be created by repositioning the basket assembly or by switching between different electrodes.

The pulsed electric field (PEF) is for instance created by electrical pulses, for example high frequency electrical pulses. The electrical pulses may be generated by a pulse generator and may be delivered to the target tissue by the electrodes which may be placed on the catheter distal tip and which may be in electrical contact with the pulse generator. The electrical pulses can be created by a wide variety of electrical pulses ranging from monophasic (single polarity) pulses to symmetrical and/or asymmetrical biphasic pulses. The pulses may be combined with extra pre-pulses for tissue conditioning or extra measurement pulses as well. Pulses can be single pulses, or they may be repeated in trains, where parameters of the pulses may vary or remain constant. Trains of pulses can be run in sequences as well. A maximal amplitude of the pulses may depend on the target tissue, electrode's size and/or electrode's distance in order to create an electric field with a maximum electric field magnitude for example between 0.1 kV to 10 kV or between 0.4 kV to 5 kV or between 0.5 kV to 2 kV per centimeter in a target tissue volume. A duration of the pulse can be from a nanosecond range to milliseconds range, for example from 2 ns to 10 ms, or from 10 ns to 5 ms or from 10 μs to 1 ms. The shape of the pulse may be for example a square, a curve similar to exponential discharge, a rectangle, a saw, a triangle or a sinusoidal shape.

The pulses can be monophasic or biphasic. Biphasic pulses can be symmetrical or asymmetrical. The pulses can repeat from 1× to 100000×. The frequency of the high frequency pulses may vary from 0.1 Hz to 10 Hz. Amplitude (Um) of the monophasic pulses can vary from 100V up to 10 kV, and the peak-to-peak amplitude of biphasic pulses may vary from 200V to 20 kV.

FIG. 16 may serve as an example of a possible part of a pulsed field ablation (PFA) protocol and as a clarification of terms and expressions regarding the PFA protocol. The PFA protocol includes a series of electrical pulses (1601) and pauses (1603, 1607, 1615). The electrical pulses (1601) may be further organized in units with a certain hierarchy like trains (TR) and bursts (B).

The electrical pulse (1601) may be defined for example by shape, amplitude (Um) with certain voltage and pulse length with time duration (t1). The pulse amplitude (Um) may be either negative or positive (the pulse may have negative voltage or positive voltage) in case of monophasic pulses. The electrical pulses (1601) may be separated from each other by an inter-pulse pause (1603), which is defined by a time duration (t2) and a voltage (Up). The voltage during the inter-pulse pause (1603) may drop to 0V or it may have a positive or negative voltage value (Up). The absolute voltage value (Up) of the inter-pulse pause is smaller than an absolute voltage (amplitude (Um)) of the adjacent electrical pulse (1601), particularly up to 50% of the amplitude (Um) of the adjacent electrical pulse. In situations where the electrical pulse has a positive amplitude (Um), the voltage value (Up) of the inter-pulse pause (1603) will stay positive between 0V and the electrical pulse (1601) amplitude (Um), and in situations where the electrical pulse (1601) has a negative amplitude (Um), the voltage value (Up) of the inter-pulse pause (1603) will stay negative between 0V and the electrical pulse amplitude (Um). An example of inter-pulse pauses (1603) with a voltage different than 0V is shown in FIG. 17 a . Biphasic pulses may be symmetrical or asymmetrical in at least one of time, amplitude or energy.

Examples of biphasic electrical pulses are shown in FIG. 17 b . The biphasic pulses may have the same amplitude (voltage) of a positive phase (1701) and a negative phase (1703) with the same duration (t10, t12) of both phases (exemplary pulse A, D), or the amplitude and/or duration (t10) of the positive phase and the amplitude and/or duration (t12) of the negative phase may differ (exemplary pulses B, C). The resulting pulses then may have the same energy in the positive and negative phases of the pulse, or the energy in the positive and negative phases of the pulse may be different. Biphasic pulses with the same energy in both phases may be called symmetrical biphasic pulses. Symmetrical biphasic pulses may be balanced (in case the duration and amplitude of both phases of the pulse are identical, or imbalanced (in cases where the amplitude and/or duration are different in each phase). Asymmetrical biphasic pulses have phases with different energies. Exemplary biphasic pulses A, B, C are without a pause between particular phases (inter-phase pauses) of the pulse, exemplary pulse D is a biphasic pulse with an inter-phase pause (1705). The duration of the inter-phase pause of the pulse may be from 0 μs to 50 μs or from 0 μs to 10 μs or from 0 μs to 5 μs.

A series or sequence of pulses in a row, with or without inter-pulse pauses may be called a train (TR). Particular trains (TR) may be characterized for example by a time duration (t4), or number of pulses and may be separated from one another by inter-train pauses (1607) with a time duration (t5) or the inter-train pause (1607) may separate a train with an individual single pulse. A series or sequence of the trains (TR) and inter-train pauses (1607) can be called a burst (B), and may be characterized for example by a time duration (t6), number of trains (TR), number of pulses or by inter-burst pause (1615) (with time duration (t7) between particular bursts (B).

As already stated above, a voltage value (Up) at the electrodes may not decrease to 0V between pulses, particularly during inter-pulse pauses (1603) but may remain at a level, where the risk of creating bubbles by electrolysis or temperature increment is either non-existent or very small, for example up to 50% of the amplitude (Um) of an adjacent electrical pulse. This may reduce an unwanted relaxation of the polar molecules as well, which may lead to shorter length of at least some parts of the PFA protocol and so increase an efficacy of the PEF therapy.

When pulses with amplitude (Um) of hundreds of volts to a few thousand volts are applied, there is a certain risk of causing a ventricular muscle depolarization and unwanted ventricular rhythms in the heart, even when applied in a heart atrium. Depolarization can be caused directly by electric field or by secondary energy induction in another device, for example a catheter, which is placed in or near either atria or ventricles or both. Setting the timing of the active sequences (individual pulses, trains and/or bursts) with pauses described below results in an effect called overdrive. The overdrive effect is commonly used in ablation catheterization procedures to suppress a risk of unwanted heart rhythms by using an external pacemaker. An advantage of the proposed PFA protocol is that the therapeutic (ablation) electrical pulses may, in a case where they cause a myocardium depolarization, also act as pace stimulation pulses for the heart, and therefore it is not necessary to use an additional pacing device (for example an external pacemaker) to synchronize pulses of the pacing device with the therapeutic pulses of the PFA protocol. This in turn means that in this case it is not necessary to use a pacing device to control the number of ventricular contractions per minute, detect the individual ventricular contractions from a surface ECG and then trigger the ablation pulses accordingly.

The duration (t8) of one cycle (1609) of a burst (B), and inter-burst pause (1615) between bursts, which is between 201 ms to 800 ms, is given by a range between the need to deliver pulses safely faster than the patient's actual heart rate (the overdrive effect) and the need to maintain heart rate at a safe level (which is stated to be approximately 220 beats per minute minus age). The cycle duration may be fixed or variable in the stated range (201 ms to 800 ms) within a PFA protocol, for example according to a sinusoidal or triangular function. The individual burst (B) may have a duration (t6) from 1 ms to 200 ms, or 30 ms to 180 ms, or 60 ms to 160 ms, which is a safe time to contract the heart chamber by an applied burst (B) of pulses, protecting ventricles from injury or unwanted rhythm. The burst (B) duration (t6) may too be fixed or variable in the stated range (1 ms to 200 ms) within a PFA protocol, for example according to a sinusoidal or triangular function.

This PFA protocol may have other positive effects on the ablation results, for example reducing the risk of causing an unwanted ventricular rhythm and/or maximized PEF application efficiency.

However an electroporation is described as the primary trigger of death of the myocardial cells after application of the PEF, but actual cell death may alternatively be caused for example by electrical breakdown of the membrane of cardiomyocytes, mitochondria or nucleus; by tearing individual cells/cardiomyocytes (or groups of cells) of the myocardium apart (for example, by damaging the intercalated discs, either directly by electric fields or by mechanical damage by hypercontraction); by damage to sarcolemma or myofibrils of muscle fiber; by depletion and insufficient production of ATP in cardiomyocytes due to hypercontraction; by loosening of intercellular junctions of cardiomyocytes; by muscle cell myolysis; by wrinkling cardiomyocytes either directly under the influence of the electric field or by mechanical damage by hypercontraction; by irreversible damage to the calcium cycle (whether by non-physiological function of the sarcoplasmic reticulum or ion pumps or calcium channels or calcium binding proteins); by calcium overload of the heart muscle-mitochondrial swelling (as a result of hypercontraction or damage to cardiomyocyte sarcolemma or non-physiological function of calcium channels); or by formation of reactive oxygen species (ROS) and subsequent oxidation of membrane phospholipids by PEF.

The electric fields may be created among one or more electrodes placed on the catheter distal tip and one indifferent electrode placed in the distance, for example on the skin of the patient. The indifferent electrode may in some aspects have a significantly larger surface than the sum of the surfaces of the active distal tip electrodes. This mode of action is usually called monopolar. Another option for creating an electric field is in a bipolar mode. In this mode the electric field arises between two or more, usually closely-placed or adjacent distal tip electrodes with different polarities. In this case the sum of the surfaces of active electrodes with the first polarity is similar to the sum of the surfaces of the active electrodes with the second polarity.

In some aspects, the electrodes (109) placed on the distal assembly may be operated in a hybrid mode of the previous two types. An example of such a mode is shown in FIG. 11 . Only the electrodes (109) placed on the distal tip (107) are used for ablation in this mode. There is a first single electrode, or group of electrodes operating in a mode with first polarity (P1) and a second single electrode or group of electrodes operating in a mode with different polarity (P2) (which may be an opposite polarity) than the operating mode of the first electrode or group of electrodes. A surface or a sum of the surfaces of the first electrode or the first group of electrodes is significantly smaller than a surface or a sum of the surfaces of the second electrode or group of electrodes. For example, there may be a third group of electrodes operating in a third mode in state of high impedance (HI), wherein the impedance of the electrodes in the third group is for example higher than 500 SI The electrodes operating in the third mode may be adjacent to the electrode or group of electrodes operating in the first mode.

One advantage of the operation of electrodes in this hybrid mode is that the generated electric field will have a more homogenous current density in comparison to bipolar mode. Another advantage of the hybrid operation mode is the electric fields created in this mode may in some aspects be able to reach deeper into the target tissue compared to bipolar mode. In case of ablation of a heart cavity, the depth of the ablated target tissue, (in one example the target tissue may comprise a myocardial tissue), may be up to 5 mm.

A variant of the hybrid mode of operation of the electrodes (109) with a group of electrodes (more than one electrode) operating in the mode with the first polarity (P1) is shown in FIG. 12 . The functional principle of this mode of operation is similar to the variant with one electrode (109) operating in the mode with the first polarity (P1). For example, the sum of surfaces of the electrodes operating in the mode with the first polarity (P1) is significantly smaller than the sum of surfaces of the electrodes operating in a mode with a different polarity (P2).

Examples with a group of electrodes (more than one electrode) operating in a mode with a first polarity (P1) can have an advantage over examples with a single electrode operating in the mode with the first polarity (P1) for example in situations where it is advantageous to reduce the size of the electrodes. Reducing the size of the electrodes can be advantageous or necessary in cases where it is necessary or desirable to increase the number of electrodes. A higher number of electrodes is desirable for example where more precise mapping of the treatment site or more precise and/or more homogenous ablation of the target tissue of the treatment site is desired. Because the treatment site can be part of a human anatomy, the overall size of the pulsed field ablation device, especially the catheter with a catheter distal tip must be restricted according to human anatomy. It follows that if more electrodes are needed for the ablation device, then for a certain number of electrodes the size of the electrodes must be limited to able to fit into the restricted dimensions of the critical parts of the pulsed field ablation device for example the catheter and/or its distal tip, and/or its basket assembly. Another advantage of the smaller size of the electrodes is that such an arrangement may help to increase a depth of the ablation.

Smaller size of the electrodes can have other advantages, for example in examples where the same electrodes are used for ablation and for measurements, it means the same electrode must be configured to deliver high voltage pulses and record measurements. For example, in measurement of ECG signals, smaller electrodes may be advantageous.

There are however some challenges associated with smaller electrodes as well. In examples including pulsed field ablation, the electric fields are for instance created by electrical pulses, for example high frequency electrical pulses generated by a pulse generator. For effective ablation of the whole target area of the treatment site, it may be important to create an electric field with a maximum electric field magnitude of several hundred volts to several kilovolts per centimeter in a target tissue volume. Using smaller electrodes means a smaller surface area of the electrodes. With a smaller surface area of the electrodes, the voltage induced on the electrode has to be higher compared to bigger electrodes with larger surface area to achieve the desired electric field density in a target tissue. Adverse effects of such a configuration may include higher density of the electric field, higher intensity of the electric field and/or possible sparking on the edges of the electrodes. However, using a chosen group of electrodes (more than one electrode) operating in the mode with the first polarity instead of one electrode operating in the mode with the first polarity can address and overcome some or all of these issues. With a well-chosen first group of electrodes operating in the mode with the first polarity together with the second group of electrodes operating in a mode with different polarity and possibly with a third group of electrodes operating in a third mode in the state of high impedance, the first group of electrodes and/or the second group of electrodes may act as virtual electrodes. That means the electrodes in the first group may act together as one virtual electrode and/or the electrodes in the second group may act as another virtual electrode. With such a configuration, the intensity and/or the density of the electric field near the electrodes may be reduced. Other positive effects of this configuration may be a reduced risk of sparking and increased depth of ablation, or increased depth of an ablated tissue at the treatment site.

The enlargement of the surface area of the electrodes in the first group and the creation of the resulting virtual electrode may cause a reduction in the voltage needed to be induced in the electrodes and/or elimination of sparking, mainly on the edges of the electrodes. However, the concept of disproportional surface areas of the electrodes in the first and the second groups of electrodes can be preserved, which means the surface area or a sum of the surface areas of the first electrode or the first group of electrodes is significantly smaller than a surface area or a sum of the surface areas of the second electrode or group of electrodes. The ratio of the surface area of the electrode or the sum of the surface areas of the electrodes in the first group to the sum of the surface areas of the electrodes in the second group of electrodes may be between 2:3 to 1:100, or 3:5 to 1:80, or 3:5 to 1:70, or 1:2 to 1:50, or 1:2 to 1:40, or 1:2 to 1:30, or 1:2 to 1:20, or 1:3 to 1:15, or 1:3 to 1:10, or 1:4 to 1:8.

Adding electrodes to the first group of electrodes operating in the mode with the first polarity may significantly reduce the intensity of the electric field near the electrodes. Using four electrodes instead of one for example in the first group of electrodes operating in the mode with the first polarity, the intensity of the electric field at the electrode surface decreases by a factor of four, while in examples where three electrodes are used, the intensity of the electric field decreases by a factor of two. This reduction in intensity may allow for the use of lower voltage on the electrodes, compared to a solution with just one electrode operating in the mode with the first polarity. The reduction may additionally or alternatively increase of the depth of the ablated target tissue by increasing an area of the electric field with a certain voltage per cm². The value of the voltage per cm² in an area of the electric field may be for example from 50 V/cm² to 3000 V/cm², or from 100 V/cm² to 1500 V/cm², or from 250 V/cm² to 1000 V/cm².

The particular electrodes on the catheter distal tip can be switched to one or more than one of the modes during the ablation. They can be switched during one ablation cycle or during several ablation cycles. The electrodes may be switched to one or more of the modes several times during one ablation cycle or during several ablation cycles. In some aspects it is even possible to have two or more groups of electrodes operating simultaneously in a mode with the first polarity and a group of electrodes operating in a different polarity, with or without electrodes operating in a state of high impedance.

A layout or spatial pattern of the electrodes on the distal tip may be created with a consideration of the hybrid mode of operation of electrodes and/or with the goal of creating virtual electrodes. Because the electrodes may be switched to one or more than one of the modes during the ablation, it is possible the resulting virtual electrodes may have different spatial shapes which means the electric fields created around and between the virtual electrodes may have different shapes with different structures of the magnetic field and/or different density and intensity of the electric field. An example of a spatial pattern of electrodes on the distal tip, specifically on the expandable basket may be seen in FIG. 13A and in FIG. 13B. FIG. 13A shows a frontal view of the basket assembly (401) with a spatial pattern of electrodes (109) suitable for creation of virtual electrodes by switching the electrodes (109) into different modes of operation with the first polarity and with the different polarity and/or with a state of high impedance.

FIG. 13B shows again a frontal view of the basket assembly (401) with a spatial pattern of electrodes suitable for creation of virtual electrodes, by switching the electrodes (109) into different modes, however this time the electrodes are placed in areas where the filaments (415) cross each other (filaments crossing points).

One possible layout of electrodes already switched into the hybrid operation mode may be seen in the FIG. 14 , which is again a frontal view of the basket assembly (401). A first group of electrodes (109) is operating in the mode with a first polarity (P1) and together creates a first virtual electrode (1401). Another group of electrodes (109) is operating in the mode with a different polarity (P2) and together creates a second virtual electrode (1403). When electrical pulses are delivered from the pulse generator (103) to the electrodes (109) in this configuration, electric fields will be created between and around the virtual electrodes (1401, 1403). Some of the electrodes (109) may be operating in a third mode, for example in a state of high impedance (HI).

The electrodes in a state of high impedance (higher than 500Ω) may help in shaping an electric field created among and around electrodes from the first group and the second group of electrodes and/or between or around the virtual electrodes. In one example, assigning a state of high impedance to electrodes which are spatially adjacent to the electrodes operating in the mode with a first polarity may have a positive effect on the shape of the electric field in a way that a portion of the electric field which is able to cause an ablation reaches deeper into the target tissue of the treatment site, compared to an operation mode without electrodes in a state of high impedance. This phenomenon may have positive effects in the quality and homogeneity of an ablation procedure. The electrodes in a state of high impedance may be spatially placed between the first group of electrodes and the second group of electrodes.

An exemplary pattern of electrodes (109) is displayed in more detail in FIG. 15A. The electrodes (109) create a pattern of repeating crosses or squares or rectangles on the filaments (415) of the braided mesh in one of the expanded configurations of the expandable basket. From this view, which is perpendicular to the tangent plane (which is touching the expandable basket for example at an intersection (1501) of four neighboring electrodes), the pattern seems two-dimensional, but in reality, it is three-dimensional, because the electrodes (109) are fixed to, or are part of the filaments (415) of the braided mesh, which creates an expandable basket, and therefore the pattern fits into the curvature of the expandable basket. This pattern of the electrodes is advantageous in embodiments using a group of electrodes operating in a mode with first polarity (P1). In this example a group of four adjacent electrodes operating in a mode with first polarity (P1) and hence creating a first virtual electrode (1401) will have either a cross shape, as indicated in FIG. 15A or a square or rectangle shape as indicated in FIG. 15B. The advantage is that both virtual electrodes (1401) created by both shapes are, in combination with a second virtual electrode, and possibly with the help of the electrodes in a state of high impedance, capable of creating electric fields having certain qualities (shape, magnitude, density, gradient of potential) suitable for the ablation of a target tissue.

FIG. 15C shows an example of a pattern of electrodes where the electrodes (109) are placed in areas where the filaments (415) cross each other (filament crossing points). An exemplary group of electrodes operating in a mode with first polarity (P1) is also shown here.

The exact shape of the pattern of electrodes partially depends on the shape of the expandable basket. It also means the pattern and the shape of the groups of electrodes creating the virtual electrodes may be different in a collapsed configuration and/or in different expanded configurations of the expandable basket. For most of the expanded configurations of the expandable basket, the rectangles and squares created by the electrodes as described above will be inclined and will be creating shapes closer to rhombuses or rhomboids. The same applies to the angles between the two imaginary lines creating a cross and passing through the electrodes, which will not be right angles in most of the expanded configurations.

When using high voltage pulses in the human body, it may be necessary to synchronize the delivery of the pulses with a cardiac cycle for safety reasons, for example in order to avoid ventricular rhythm. The pulsed field ablation device can incorporate or use a means for such a synchronization including triggering of the pulse delivery by this synchronization means. The synchronization means can be for example an ECG device. 

The invention claimed is:
 1. An ablation device for pulsed field ablation of a tissue by pulsed electric field, the device comprising: a catheter configured for insertion into a heart of a patient comprising a set of electrodes; and a pulse generator configured to generate electric pulses, the pulse generator electrically coupled to the set of electrodes; wherein the set of electrodes is configured to provide pulsed electric fields from the electric pulses causing ablation of a tissue within the heart of the patient; wherein the set of electrodes comprises a first electrode configured for operation in a mode of a first polarity, a second electrode configured for operation in a mode of a second polarity different than the first polarity, and a third electrode configured for operation in a mode of a state of high impedance; and wherein the set of electrodes comprises at least one electrode configured to be switched between at least two of the modes during an ablation.
 2. The ablation device according to claim 1, wherein the third electrode is configured for operation in a mode of a state of impedance higher than 500 Ω.
 3. The ablation device according to claim 1, wherein a ratio of a surface area of the first electrode to a surface area of the second electrode is in a range from 2:3 to 1:100.
 4. The ablation device according to claim 1, wherein the set of electrodes comprises at least two second electrodes configured for operation in the mode of the second polarity different than the first polarity.
 5. The ablation device according to claim 4, wherein the set of electrodes comprises at least two third electrodes configured for operation in the mode of the state of high impedance.
 6. The ablation device according to claim 4, wherein a ratio of a surface area or sum of the surface areas of the at least one first electrode to a sum of a surface areas of the at least two second electrodes is in a range from 2:3 to 1:100.
 7. The ablation device according to claim 1, wherein the third electrode is spatially adjacent to the first electrode.
 8. A catheter for pulsed field ablation of a tissue by pulsed electric field, the catheter configured for insertion into a heart of a patient comprising: a set of electrodes; the set of electrodes configured to provide pulsed electric fields causing ablation of a tissue within the heart of the patient; wherein the set of electrodes comprises a first electrode configured for operation in a mode of a first polarity, a second electrode configured for operation in a mode of a second polarity different than the first polarity, and a third electrode configured for operation in a mode of a state of high impedance; and wherein the set of electrodes comprises at least one electrode configured to be switched between at least two of the modes during an ablation.
 9. The catheter according to claim 8, wherein the third electrode is configured for operation in a mode of a state of impedance higher than 500 Ω.
 10. The catheter according to claim 8, wherein a ratio of a surface area of the first electrode to a surface area of the second electrode is in a range from 2:3 to 1:100.
 11. The catheter according to claim 8, wherein the set of electrodes comprises at least two second electrodes configured for operation in the mode of the second polarity different than the first polarity.
 12. The catheter according to claim 11, wherein the set of electrodes comprises at least two third electrodes configured for operation in the mode of the state of high impedance.
 13. The catheter according to claim 11, wherein a ratio of a surface area or sum of the surface areas of the at least one first electrode to a sum of a surface areas of the at least two second electrodes is in a range from 2:3 to 1:100.
 14. The catheter according to claim 8, wherein the third electrode is spatially adjacent to the first electrode.
 15. A catheter for pulsed field ablation of a tissue by pulsed electric field, the catheter configured for insertion into a heart of a patient; wherein the catheter comprising a set of electrodes couplable to a pulse generator, wherein the pulse generator is configured to generate electric pulses; the set of electrodes configured to provide pulsed electric fields from the electric pulses causing ablation of a tissue within the heart of the patient; wherein the set of electrodes comprises a first electrode configured for operation in a mode of a first polarity, a second electrode configured for operation in a mode of a second polarity different than the first polarity, and a third electrode configured for operation in a mode of a state of high impedance; and wherein the set of electrodes comprises at least one electrode configured to be switched between at least two of the modes during an ablation.
 16. The catheter according to claim 15, wherein the third electrode is configured for operation in a mode of a state of impedance higher than 500 Ω.
 17. The catheter according to claim 15, wherein a ratio of a surface area of the first electrode to a surface area of the second electrode is in a range from 2:3 to 1:100.
 18. The catheter according to claim 15, wherein the set of electrodes comprises at least two second electrodes configured for operation in the mode of the second polarity different than the first polarity.
 19. The catheter according to claim 18, wherein the set of electrodes comprises at least two third electrodes configured for operation in the mode of the state of high impedance and wherein a ratio of a surface area or sum of the surface areas of the at least one first electrode to a sum of a surface areas of the at least two second electrodes is in a range from 2:3 to 1:100.
 20. The catheter according to claim 15, wherein the third electrode is spatially adjacent to the first electrode.
 21. The catheter according to claim 15, wherein the catheter is configured to be manipulated from a collapsed configuration to at least one expanded configuration.
 22. The catheter according to claim 15, wherein the catheter comprising an expandable basket; and wherein the set of electrodes is positioned on the basket.
 23. The catheter according to claim 22, wherein the expandable basket comprising a plurality of filaments comprising an electrically non-conductive material; and wherein the set of electrodes is positioned on the plurality of filaments.
 24. An ablation device for pulsed field ablation of a tissue by pulsed electric field, the device comprising: a pulse generator configured to generate electric pulses, the pulse generator configured to be electrically coupled to a set of electrodes configured to provide pulsed electric fields from the electric pulses, the pulsed electric fields configured to cause an ablation of a tissue within a heart of a patient; wherein the device is configured to switch a first electrode from the set of electrodes to a mode with a first polarity, a second electrode from the set of electrodes to a mode with a second polarity different than the first polarity, and a third electrode from the set of electrodes to a mode of a state of a high impedance; and wherein the device is configured to switch at least one electrode from the set of electrodes between at least two of the modes during an ablation.
 25. The ablation device according to claim 24, wherein an impedance in the mode of a state of a high impedance is higher than 500 Ω.
 26. The ablation device according to claim 24, wherein a ratio of a surface area of the first electrode to a surface area of the second electrode is in a range from 2:3 to 1:100.
 27. The ablation device according to claim 24, wherein the device is configured to switch at least two second electrodes from the set of electrodes to the mode of the second polarity different than the first polarity.
 28. The ablation device according to claim 27, wherein the device is configured to switch at least two third electrodes from the set of electrodes to a mode of state of a high impedance.
 29. The ablation device according to claim 27, wherein a ratio of a surface area or sum of the surface areas of the at least one first electrode to a sum of a surface areas of the at least two second electrodes is in a range from 2:3 to 1:100.
 30. The ablation device according to claim 24, wherein the third electrode is spatially adjacent to the first electrode. 